Ribbed frusto-conical lining for tube mills



March 10, 1959 P. FOBELETS 2,876,957

RIBBED FRUSTO-CONICAL LINING FOR TUBE MILLS Filed on. 10, 1955 a P INVENE; i iTlli 1 Mali i W f Q RIBBED FRUSTO-CONICAL LINING FOR TUBE MILLS Paul Louis Fobelets, Boitsfort, Belgium,

Societe Anonyme Usines Emile gium, a company of Belgium Application October 10, 1955, Serial No. 539,547

assiguor to Henricot, Etienne, Bel- Claims priority, application Germany October 23, 1954 Q 6 Claims. (Cl. 241-183) This invention relates to cylindrical grinding mills of the kind in which the material to be ground travels from a supply point arranged at one end thereof to a discharge point, where it leaves the mill in the ground state.

Such tube mills which are used for widely differing purposes, especially for the grinding of cement, are interiorly lined with hardened steel plates provided with projections which grip the material as well as the grinding bodies upon rotation of the mill thereby raising them to a certain extent whereupon they fall down and by impact and friction disintegrate the material to be ground.

Originally the interior of such mills was made continuously cylindrical. Later it was found that from the point of view of efiiciency it is advantageous to subdivide the mill into a plurality of subsequent sections and to use in these sections grinding bodies the size of which gradually diminishes in consecutive sections in the direction of travel of the material.

In order to ensure that the grinding bodies remain in their respective sections, the sections are usually separated by walls arranged perpendicular to the axis of the mill with orifices allowing only the ground material to pass therethrough.

The number of walls required in these types of mills increases the weight and costs considerably. Moreover the walls are subject to wear, necessitating frequent renewal of them. Further frequent regrading of the grinding bodies in the various sections is required, since they wear out quickly and lose their prescribed dimensions.

With the aim to avoid these disadvantages, it has later been proposed to subdivide the mill into sections not by intermediate walls, but by making each section frustoconical in shape narrowing in the direction of travel of the material to be ground so that a number of subsequent converging surfaces are formed, separated one from the other by steep radial steps.

By this construction the grinding bodies are retained in their proper sections and the premature movement of the material to a subsequent section is prevented, but only so long as the grain size is relatively small sandlike or less than about ,4; inch size. A material of coarser grain size however behaves like grinding bodies of equal weight. Consequently the larger constituents of the material to be ground, having a lower densitythan the grinding bodies, proceed into sections of the mill containing grinding bodies too small to exert a sufiicient impact on elements of this size.

According to a further proposition these disadvantages are at least partially avoided by forming the frustoconical surfaces not as plain surfaces or surfaces cor rugated in transverse direction, but of a plurality of projections, the heads of which follow the general frustoconical formation of the section. By this arrangement of the projections the distances being sulficiently small to prevent the grinding bodies from becoming jammed between them, the coarser grains of the material are retarded and thereby prevented to migrate to following.

sections before being sulficiently disintegrated.

The projections raise the material to be ground to-;

gether with the grinding bodies without any relative movement taking place between the grinding bodies and the lining during this lifting. That means that any sliding of the material to be ground on the grinding surface and consequently the unnecessary expenditure of power for a repeated raising of the material is obviated. Moreover by raising the grinding bodies 'to a higher level their impact on the material becomes more efiicient.

This however offers the disadvantage that due to friction from the projections the return of the grinding bodies to the" lowest point of the frusto-conical sections does not take place quickly enough, which could be" detrimental to the output of such mills. By the present invention all the disadvantages of the known constructions of tube mills are avoided without introducing new drawbacks whilst simultaneously increasing the output of the mill and reducing wear.

According to the invention the. grinding surface of the lining of the frusto-conical zones formed of a plurality of plates of hardened steel is constituted by longitudinal ribs of cam-like profile, separated from one another by longitudinal grooves of a width not allowing grinding bodies to penetrate into them, adjacent parts of the surfaces of each two longitudinal ribs being so inclined with respect to one another as to form runways for the grinding bodies leading towards the lowest point of the fruso-conical section. are interrupted by transverse grooves subdividing the ribs in distances greater than the width of the ribs.

By this construction the considerable lift exerted on the material to be ground and the grinding bodies by the rotation of the mills is maintained, and at the same time the return movement of the grinding bodies is accelerated. The subdivision of the ribs by transverse grooves at comparatively large intervals prevents the propagation of undesirable deformations due to the impact of the grinding bodies into neighboured areas of the lining plate and improves the cold working by the impact of the grinding bodies on the relatively big grinding surface consisting of the total area isolated from one another by the grooves.

On the crossing point of the transverse grooves with the longitudinal grooves local enlargements are formed,

- wherein, due to small grinding bodies or larger bits of material in the process penetrating and becoming jammed into them, obstructions are formed which exert" on the material a retardingeflect which may be desirable in certain circumstances.

According to a particular feature of the invention the surface of the ribs in the neighborhood of the longitudinal grooves is flat so that between these faces'and the adjacent grooves edges are formed. By this arrangement the lifting effect of the runways formed by opposite areas of adjacent ribs is no longer dependent on the diameters of the grinding bodies. The top surfaces of the ribs are however preferably slightly cambered.

The depth of the longitudinal and preferably also of.

the transverse grooves should be relatively considerable .and preferably larger than half the width of a rib, in order to secure sufficient separation of the ribs from one another, and to prevent any penetration of the grinding bodies down to the bottom of the grooves. can taper slightly inward from the top to the bottom.

The transverse grooves of neighbouring ribs are preferably arranged offset to one another so that a T-shape arrangement resultsat their crossing with the longitudinal grooves.

According to a further feature of the invention the .ribs are reinforced in their area between the transverse Patented Mar. 10, 1 959.

Preferably these runways] of the individual parts The grooves grooves opposite to a' transverse groove of the adjacent rib; The'object ofthese'reinforcements is to obtain a" snake-like movement of the grinding bodies rolling down andalso to retard jamming jof the grinding bodies when they become smaller. owing to wear;

According to a further feature of the. invention it' has,also been found advantageous for an even distribution of'the grinding bodiesto block alternate or all of the longitudinal grooves just beforejthe end of the frustoconical section is reached, and by this arrangernent to stop the grinding bodies just clear ofthe bottom.

Further features and details ofthe inventionwill'bep come clear from the following description of arcylindrical' grinding mill provided with a liningaccording to the in v vention, given byway of example, with reference to the accompanying drawings, in which;

Figure l is a longitudinal sectionof a, mill constructed according to the invention;

Figure 2 is a plan view of a lining plate, that is, vEltde}.

veloped projection; thereof in a, horizontal plane tangent to the mill shell cylinder;

FigureS is a section along the ,lineIlI-Ill of Figure 2 in whichthe direction arrows .(line ofsight) liein the.

planeot the liner plate, that is, the section is perpendicular to the plane of Figure 2;

Figure 4 isa section along the line -IV-'IV of Figure 2. The tube mill illustrated in Figure 1 is in general of cylindrical shape. The material to be ground is fed inat.

one end 2, which in the figure ison the .lefthand side and discharged at the oppositevend .at El.v Theshellfitof. the, mill, encloses the consecutive'sections, 53 55, 5"

formed ofaplurality. of liner. plates 8 which internally.

tive, Sections. One of the plates 8 from which the linings ot'thesections are composed which have dimensions of, forexample, 500 x 250 millimetres isshown in detail in Figures 2 to 4. The plates present the. substantially con tinuous ribs '7', '7", 7".separated by the longitudinal grooves 6, 6", 6. The apparent convergence or taper of the plate 8 and the longitudinalgrooves 6', 6'-', and .6 in'Figure 2 isrdneto the planar projection of the curved inclined surface. of the p lata that is, the developmentof the surface on a horizontalplanetangent to. the mill ,shell cylinder. Actually, the plate is rectangular in outline and the longitudinal groovesare parallel to one another, the plan projection providing anvillusion of con: vergence. The ribs 7', 7", 7 are interrupted by transverse grooves 8, 8", 8" width thereof. The width of the grooves 6, 6f, 6" thev profileot which tapers preferably towards thebottom otthe grooves, is so dimensioned that the grindingbodies cannot penetrate into them deeply enough to become jammed. Their depth amounts to, more than half the width of the ribs 7, 7", 7", which in turn is a multiple of the width of the grooves. Eachrib is shapedwith a slightly .camberedapex portion,9;which is followed on. both sides by straight flanks 10, 10", which end in a:

sharp edge confining the grooves. At the junctionofithc transverse grooves 8,, 8", 8" of adjacent ribs-ofiset;with,. respect to one another, according to the preferred; modification with the longitudinal grooves, T-shaped enlarge-,-

. at intervalslarger than the ments are formed. The localreiniorcements 11 provided 1 on thelongitudinal ribs7 oppositeeach transverse groove impart a somewhat. snake-like movementto the grindingbodies rolling: down said grooves. InFigure-Z, the reinforcing elements 11 appear curvedwith respecttodongitudinalribs7, 7" and 7'. However, this;is an illusion created by the projection development of Figure 2, and.v

as,shown in I Figure- 4, the elements 11 extend straight cmssthenbsurface.

In the plates holes 12 are provided through which extend the attachmentscrews. These holes form recesses on the surface of the plates;;which recesses act similarly to the crossing points of the transverse and the longitudinal grooves; they are preferably arranged in line with the grooves. The screw heads are completely sunken and are therebyprotected against. damage .by the grinding bodies.

At the left hand end of the plate, in Figure 4 a projection 13 is provided by means of'which arrangement, every second groove is blocked, so that the grinding bodies are stopped before reaching the end of the plate. By this means ,a betterdistributionot the grindingbodies is attained.

The advantages-of a tube mill of thetype" described according to the invention, are as follows:

(1) Within the mass of the grinding bodies the desirable tight packing is. attained.

(2) Rolling of the grinding bodies the diameter of.

which. corresponding approximately to the distance between theapices of two adjacent ribs, along the grooves is facilitated. The lifting efiect on .the grindingbodiesin the circumferential sense is fully maintained.

(3) Owing to the isolation of the effective grinding surfaces from one another by the subdivision of the longitudinal ribs by the transverse grooves preferably arranged offset with respect to one another. The effect of the impact of the grinding bodies on the material tobe ground is fully utilized, the cold'hardening etfect of the impact being localised, but also obtained in its full extent without creating flow and deformations.

(4) Due to the flat running faces formed on the ribs, the carrying-along efiect in the circumferentialdirection is substantially independent of the diameter of 'the, grindfrom the scope of the invention as defined in the appended claims. For example the invention can be appliedalso to mills .with central discharge, having. frusto-conicallin: ings tapering from both ends of the mill towards the discharge point.

What I claim is:

l. A lining for a ball mill comprising successive frustoconical sections narrowing in the direction of the flow of material through the mill and being separated by circular abrupt transverse steps, the lining of each ofsaidfrustoconical sections being composed of anumber of. indi.-.. vidual plates, each plate comprising a soleplate-provided with a dense array of anvil means having cambered top surfaces, said anvil means being closely grouped in lines lengthwise substantially parallel with one another, trans-.

verse intervals between said anvil means preventing thev entry of media, said lines in turn being disposed vside by side with longitudinal intervals constituted by continuous. grooves, and forming between themv uniformand smooth runways for a downward rolling movementin a longi-,. tudinal direction of the media impacting onsaid runways,

2. A lining according to claim 1 in which the anvil] means have top surfaces cambered at the apex portion followed on both sides by straight flanks which constitute the impact-receiving working surface.

3. A lining for a ball mill comprising successive frustoconical sections narrowing inthe direction of theflo'w of material through the mill and being separated by circular abrupttransverse. steps, the lining of each of said frustoconical sections being composed of a number of indi vidual plates, each plate comprising asoleplate provided'with a dense array ofianvil means having cambered top surfaces; said anvil ameans being closely grouped "in aavaos'r lines lengthwise of the liner, substantially parallel with one another, transverse intervals between these anvil means not allowing entry of media, said lines in turn being disposed side 'by side with longitudinal intervals constituted by continuous grooves, said grooves and said transverse intervals between the anvils having a total depth (measured from top to bottom levels of the anvils) in excess of one half of the width of the anvil means, and the groove width being so restricted as to make them also unable to catch media, the adjacent portions of the top surfaces of anvils in adjacent lines forming uniform and smooth runways for a downward rolling movement in a longitudinal direction of the media impacting on said runways.

4. A lining according to claim 3 in which the transverse intervals between individual anvils are offset with regard to one another in adjacent lines of anvils.

5. A lining for a ball mill comprising successive frustoconical sections narrowing in the direction of the flow of material through the mill and being separated by circular abrupt transverse steps, the lining of each of said frusto-conical sections being composed of a number of individual plates, each plate comprising a sole plate provided with a dense array of anvil means having cambered top surfaces, said anvil means being closely grouped in lines lengthwise of the liner, substantially parallel with one another, transverse intervals between them being ott- 6, set with regard to one another in adjacent lines of anvils, and reinforcements being provided on the body of each anvil opposite the intervals on neighbouring lines for the purpose of preventing the entry of media and thereby facilitating rolling-down of media along the slopes of the liner, said lines in turn being disposed side by side with longitudinal intervals constituted by continuous grooves, also unable to catch media and forming between them uniform and smooth runways for a downward rolling movement in a longitudinal direction of the media impacting on said runways.

6. A lining according to claim 5 in which alternate grooves are blocked by projections spaced from the discharge end of the section whereby the grinding bodies are stopped before reaching the end of the plate.

References Cited in the file of this patent UNITED STATES PATENTS 689,347 Hundeshagen Dec. 17, 1901 1,541,114 Carman June 9, 1925 1,872,036 Hardinge Aug. 16, 1932 2,367,464 Henricot Jan. 16, 1945 FOREIGN PATENTS 129,293 Germany Mar. 3, 1902 576,468 Great Britain Apr. 5, 1946 699,605 Great Britain Nov. 11, 1953 

